1. Field of the Invention
This invention relates to a method for the production of a rare-earth element/cobalt magnet powder substantially composed of (1-5) single phase by a reduction diffusion process, the magnetic powder showing excellent magnetic properties and is suitable for a resin magnet.
2. Description of the Prior Art
A rare-earth/cobalt magnetic powder substantially composed of (1-5) phase for use in a resin magnet has a sufficiently small particle diameter to display high magnetic properties and proves advantageous in compatibility with resin and in flowability and homogeneity required during the blending and molding works as compared with a magnetic powder substantially composed of (2-17) phase. Thus, it has found favorable acceptance. As a means of producing a magnetic powder substantially composed of (1-5) phase there has been adopted the so-called reduction-diffusion method, which comprises mixing the oxide of a rare earth element, a reducing agent such as metallic calcium, and cobalt powder, placing the resulting mixture in a container and heating it in an atmosphere of an inert gas under atmospheric pressure at 900.degree. C. to 1,100.degree. C., adding the resultant reaction product to water, thereby producing a slurry, and treating the slurry with water and an aqueous acid solution.
This method, however, affords as a reaction product of reduction-diffusion nothing other than a magnetic powder such as to acquire a mean composition of the (1-5) phase. When magnetic powder obtained by this method is finely comminuted and press molded, then thermally treated for improvement of its magnetic properties, and used for a sintered magnet, this the magnet proves more advantageous in magnetic properties and cost of production than a magnet using a magnetic powder obtained by the conventional electrolytic method or solution method. When the magnetic powder mentioned above is used in its unmodified state for a resin magnet, since it has not yet undergone the thermal treatment for the improvement of magnetic properties and further since this thermal treatment can no longer be adopted after the magnetic powder is mixed with resin, the produced resin magnet has the disadvantage that the magnetic properties thereof, particularly residual flux density, are notably inferior to those of a resin magnet made of the magnetic powder which has undergone the thermal treatment.